title: Involvement of endothelial ephrin-B2 in adhesion and transmigration of EphB-receptor-expressing monocytes.
abstract: The vascular endothelium is a crucial interface that controls the recruitment of circulating leukocytes. Based on the luminal expression of the ephrin-B2 ligand by endothelial cells (ECs) and the expression of EphB receptors (EphBRs) by circulating monocytes, we hypothesized that EphBR-ephrinB interactions are involved in monocyte adhesion. Adhesion experiments with monocytic cells were performed on ECs that overexpressed either full-length ephrin-B2 or cytoplasmically truncated ephrin-B2 (DeltaC-ephrin-B2). Atomic force microscopy confirmed similar adhesive strengths of EphBR-expressing J774 cells to ECs that either overexpressed full-length ephrin-B2 or truncated DeltaC-ephrin-B2 (1-minute interaction). Yet, adhesion experiments under static or flow conditions for 30 minutes demonstrated the preferential adhesion of monocytic cells to ECs that overexpressed full-length ephrin-B2 but not to DeltaC-ephrin-B2 or to ECs that had been mock transduced. Adhesion was blocked by ephrin-B2-specific and EphBR-specific antibodies. Correspondingly, adhesion of EphB4-receptor-overexpressing monocytes to ephrin-B2-positive ECs was further augmented. Trafficking experiments of cell-surface molecules revealed that, prior to internalization, the resulting EphB4-receptor-ephrin-B2 complex translocated from the luminal surface to inter-endothelial junctions. Lastly, full-length ephrin-B2 in ECs was also involved in monocyte transmigration. Collectively, our study identifies a role of EphBR-ephrinB interactions as a new step in the cascade of events leading to monocyte adhesion and transmigration through the vascular endothelium.
authors.affiliation: Joint Research Division Vascular Biology, Medical Faculty Mannheim, University of Heidelberg, and German Cancer Research Center (DKFZ-ZMBH Alliance), Heidelberg, Germany.
authors.forename: Dennis
authors.initials: D
authors.lastname: Pfaff
authors.forename: Mélanie
authors.initials: M
authors.lastname: Héroult
authors.forename: Maria
authors.initials: M
authors.lastname: Riedel
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Reiss
authors.forename: Robert
authors.initials: R
authors.lastname: Kirmse
authors.forename: Thomas
authors.initials: T
authors.lastname: Ludwig
authors.forename: Thomas
authors.initials: T
authors.lastname: Korff
authors.forename: Markus
authors.initials: M
authors.lastname: Hecker
authors.forename: Hellmut G
authors.initials: HG
authors.lastname: Augustin
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D002460:Cell Line; D002465:Cell Movement; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000502:physiology*; D036388:Ephrin-B2 / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D009000:Monocytes / Q000502:physiology*; D011485:Protein Binding; D036183:Receptor, EphB2 / Q000235:genetics / Q000378:metabolism*; D036224:Receptor, EphB4 / Q000235:genetics / Q000378:metabolism*
chemical_list: D036388:Ephrin-B2; D036183:Receptor, EphB2; D036224:Receptor, EphB4